langchain-ai/langgraph · error · RuntimeError

Protocol transport is closed.

Error message

Protocol transport is closed.

What it means

Error "Protocol transport is closed." thrown in langchain-ai/langgraph.

Source

Thrown at libs/sdk-py/langgraph_sdk/stream/transport/sync_ws.py:54

        ping_timeout: float | None = 20.0,
    ) -> None:
        self._client = client
        self.thread_id = thread_id
        self._commands_url = (
            commands_path or f"/threads/{_quote_path_param(thread_id)}/commands"
        )
        self._stream_path = (
            stream_path or f"/threads/{_quote_path_param(thread_id)}/stream/events"
        )
        self._default_headers: dict[str, str] = dict(headers or {})
        self._connect = connect
        self._ping_interval = ping_interval
        self._ping_timeout = ping_timeout
        self._closed = False

    def send_command(self, command: dict[str, Any]) -> dict[str, Any] | None:
        if self._closed:
            raise RuntimeError("Protocol transport is closed.")
        merged_headers = {**self._default_headers, "content-type": "application/json"}
        response = self._client.post(
            self._commands_url,
            content=orjson.dumps(command),
            headers=merged_headers,
        )
        response.raise_for_status()
        if response.status_code in (202, 204):
            return None
        payload = orjson.loads(response.content)
        if not isinstance(payload, dict) or "id" not in payload:
            raise RuntimeError("Protocol command did not return a valid response.")
        return payload

    def open_event_stream(self, params: dict[str, Any]) -> SyncEventStreamHandle:
        if self._closed:
            raise RuntimeError("Protocol transport is closed.")
        closed = False

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/sdk-py/langgraph_sdk/stream/transport/sync_ws.py:54 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langgraph@38031739e5 (2026-08-26). Data as JSON: /api/errors/3aff3b3f93d20d0d. Report an issue: GitHub.